Many different types of devices have been constructed which can act to prevent the formation of ice on the surface of a body of water and thus prevent ice damage to platform pilings, docks or pier pilings, boat hulls, etc., during cold times of the year. However, some of the known devices are quite complicated and expensive to manufacture, some are not useful in various applications, and some are simply not very effective.
Various types of ice-formation-preventing devices which function by mechanically breaking the ice as it begins to form are known. Such devices are shown, for example, in Schirtzinger, U.S. Pat. No. Re. 28,332; in Stone, U.S. Pat. No. 3,807,179; and in Lichtenberger, U.S. Pat. No. 4,077,225. However, these devices are both complex in construction, expensive, and not at all practical for non-commercial use.
Other types of ice-formation-preventing devices are known which function by heating the surface of the water in contact with the cold air thereabove. One such device which is shown in Bogosh, U.S. Pat. No. 4,127,992, involves the use of a hollow piling containing an anti-freeze solution. The lower end of the hollow piling is pounded down to extend to a significant degree into the bed at the bottom of the body of water around the dock, and the upper portion of the hollow piling is heated due to the anti-freeze solution circulating in the piling. This circulation acts to transfer latent ground heat to the upper portion of the hollow piling. Thus, since the piling itself will be heated to some extent, the water around the piling will be theoretically heated sufficiently to maintain a fluid interface between the piling and the ice forming therearound. However, this system requires the use of special hollow pilings which become an integral part of the dock which it supports, and thus is not portable or practical for use in preventing ice formation around existing docks. A device which uses the same anti-freeze circulation principles as Bogosh, but which is quite differently constructed, is shown in Baer, U.S. Pat. No. 3,618,569.
In Gross, U.S. Pat. No. 3,109,288, an ice-formation-preventing device is shown which comprises an electric motor which is mounted on the bed at the bottom of a body of water, this motor operating to suck air through an air line (which is connected at one end to the motor and at its opposite end to a float which keeps it exposed to the air above the surface of the body of water), and thereafter injecting the air in a column of water created by rotation of a propeller which is mounted on the motor. Operation of the motor causes the propeller to generate a column of water moving below and (preferably) parallel to the surface of the water, as well as air to be sucked downwardly through the air line so as to form bubbles in the column of water. Since the bubbles in the water column will cause the column to have a reduced density, the column will slowly rise to the water's surface, thereby causing the deeper, warmer water to rise to the surface and prevent ice formation. However, it is not practical to continuously maintain an electric motor below the surface of a body of water since, for one thing, over a period of time leaking seals will ultimately cause a malfunction of the motor and possibly serious damage to its internal parts.
In Clarke, U.S. Pat. No. 3,170,299, ice formation around a piling is prevented by placing a tubular device therearound, the device including a sleeve formed of a material having a high thermal conductivity such as copper or aluminum and a buoyant ring bonded to the outer upper portion of the sleeve. Due to the laws of heat conductivity, heat from the water of the lower strata of the body of water around the piling will be conducted upwardly through the sleeve so as to heat the water between the sleeve and the piling theoretically sufficiently to keep it from freezing. The buoyant ring keeps the tubular device in an appropriate position around the piling based on the surface level of the water therearound. However, since the sleeve must be made of a high thermal conductivity metal such as copper or aluminum, such materials will eventually corrode as a result of their exposure to the water therearound and over a period of time will become seriously damaged. Thus the device's durability is not terribly good.
In Lamb, U.S. Pat. No. 3,193,260 a complicated ice-formation-preventing device is shown which requires the pumping of air to a manifold below a casing member having a curved lower wall, the upwardly moving air bubbles discharged from the manifold moving over the curved lower wall of the casing member so as to create an upward movement of warm sub-surface water to the water's surface. However this device is quite complicated to construct and somewhat cumbersome to use. A somewhat similar device is shown in Cramer, U.S. Pat. No. 3,667,873; however, this device suffers some of the same disadvantages as noted with respect to the Gross patent.
In Sare, U.S. Pat. No. 3,373,821, an ice-formation-preventing device is shown which includes a submerged propeller rotated by a shaft connected to a wind-operated motor mounted on posts imbedded in the bed of a pond. The propeller creates an upflow of lower, warmer water to the surface so as to prevent ice formation. However, this device does not adapt itself to variations in the surface level of the water in the pond and is not easily portable from one location to another.
Finally, in Bruce, U.S. Pat. No. 3,686,887, a tubular device is shown which is positioned around the bottom of a piling and which is rotated so as to suck water from above the adjacent bed of the body of water and circulate it upwardly around the piling and then tangentially away from a higher up portion of the piling. This device, however, instead of being intended to pump warm water upwardly to the water's surface so as to prevent ice formation, is intended only to prevent particulate erosion from around the bottom of the piling. Thus it must always be hollow and positioned around a stationary and non-rotating piling member.
It is an object of the present invenion to provide an ice-formation-preventing device which is simple in construction, easy to service, portable, and which can be made of inexpensive and non-corrosive materials.
It is also an object of the present invention to provide an ice-formation-preventing device which can be attached to a rotatable shaft stationary attached to a platform such as a dock or pier and which can accommodate variations in the surface level of the water without need for continuous repositioning of the shaft.